The cavity or channel within a tube or tubular organ.
In the International System of Units, the derived unit of luminous flux; the light that is emitted in a solid angle of one steradian from a source of one candela. Symbol: lm.
The cavity bounded by a plant cell wall.
The bore of a tube such as a hollow needle or catheter.
A small opening in a membrane; a surgically constructed opening, especially one in the abdominal wall that permits the passage of waste after a colostomy or ileostomy.
One of the tiny pores in the epidermis of a leaf or stem through which gases and water vapor pass.
A mouthlike opening, such as the oral cavity of a nematode.
An artificial anus.